Stump mics back in focus after Rabada ban

South Africa paceman Kagiso Rabada's Test suspension for his foul-mouthed send-off of Ben Stokes on Saturday has drawn mixed responses from the cricket world, and again raised questions of television broadcasters' use of the stump mic.

A fired-up Rabada's not-so-subtle message for the England allrounder was there for all to hear on day two of the first Test at Lord's, with the stump mic clearly picking up the Protea quick telling Stokes to 'f*** off'.

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The International Cricket Council was swift in its response to the incident, slapping the Protea with one demerit point for a Code of Conduct breach. That was enough to warrant a one-Test ban, having already picked up three demerit points following a clash with Sri Lanka's Niroshan Dickwella during a Cape Town ODI in February.

The fiery Proteas pace ace also gave Test debutant Nic Maddinson a send-off in last summer's Adelaide Test which passed without action from the ICC.

Rabada was clearly seen on the Wide World of Sport coverage shouting at Maddinson after bowling him, but no stump mic audio was heard of the exchange, and no Code of Conduct charge from the ICC was forthcoming.

Former England captain Michael Vaughan was dismayed at the ICC's decision, suggesting South Africa's sluggish over-rates should be of greater concern to the governing body.

Ex-Australia allrounder Tom Moody concurred, saying the Trent Bridge crowd and television viewers would be the biggest victims in the ICC's call to strip the Proteas of their premier pace weapon for the second Test in a series already missing star players AB de Villiers and Dale Steyn, as well as Faf du Plessis for this first Test.

But commentator and former England coach David Lloyd took the opposing view, suggesting the ban may encourage Rabada to show greater respect for his victims in future.

No stranger to some on-field banter himself back in his pomp, former Australia tearaway Mitchell Johnson agreed he might not have played as many of his 73 Tests had the same hard-line stance been taken in the "olden days".

The incident brought back memories of former Australia captain Michael Clarke's infamous sledge to England quick Jimmy Anderson during the 2013-14 Ashes, where the viewing public got a brief taste of the colourful language that sometimes accompanies a heated contest.

Clarke was overhead on the stump telling Anderson, who'd confronted Test debutant George Bailey at short-leg, to face up to a fiery Johnson instead and "get ready for a broken f****n arm" at the Gabba. The skipper wold later apologise for his comments and was fined 20 per cent of his match fee by the ICC.

For their part, broadcasters Channel 9 also admitted fault for airing Clarke's foul-mouthed sledge, labelling it a "rare and isolated error".

Johnson last year called on stump mics to be turned off after another Australia fast bowler, this time Josh Hazlewood, landed in hot water when a curse uttered in frustration again wasn't muted on a live broadcast in a New Zealand Test.

Hazlewood pleaded guilty to dissent and parted with 15 per cent of his match fee during the second Test in Christchurch, but the incident drew a sharp rebuke from the Australian fast-bowling cartel, including Johnson and ex-teammate Ryan Harris.

"It is a little bit (disappointing conversations don't stay on the field)," fellow quick Jackson Bird said at the time.

"We're all for having technology in the game and all the new technology that comes out every year is great and great for the viewers at home.

"But I don't see why the stump mics need to be broadcast to the whole world. I'm not sure why they were (today)."

The ICC introduce the demerit point system in September 2016. Four demerit points in a 24-month period equates to a  ban for one Test or two limited-overs matches.